1. Field of the Invention
The present invention relates to an apparatus for stacking a cassette, and more particularly, to an apparatus which temporarily stacks a cassette which holds glass that is part of a liquid crystal display (LCD) device in order to perform various processes while moving the cassette between the processes, and a method of fabricating an LCD device using the same.
2. Description of the Related Art
The demand for information displays and portable information media is growing everyday. In response to this demand, research and commercialization efforts have been directed toward light and thin flat panel display (FPD) devices which replace a cathode ray tube (CRT) that are currently used for various display devices. Particularly, of the FPD devices, a liquid crystal display (LCD) device displays an image using the optical anisotropy of liquid crystals. Displays having LCD devices have excellent resolution, color display and image quality. As a result, LCD devices are used in many applications, such as notebook computers, desktop monitors and the like.
A LCD device will now be described in further detail. A LCD device includes a LCD panel having a driving circuit unit, a back light unit behind the LCD panel that emits light to the LCD panel, a mold frame and a case that supports the back light unit and the LCD panel.
The LCD panel includes a color filter substrate, an array substrate and a liquid crystal layer formed between the color filter substrate and the array substrate.
The color filter substrate includes a color filter having red, green, and blue (R, G and B) sub color filters for implementing colors. The color filter substrate also has a black matrix formed between the sub color filters that blocks light transmitted through the liquid crystal layer. Additionally, the color filter substrate has a transparent common electrode that applies a voltage to the liquid crystal layer.
The array substrate includes a plurality of gate lines arranged lengthwise on the substrate and a plurality of data lines arranged widthwise on the substrate. The plurality of gate lines and data lines form a plurality of pixel regions. Thin film transistors (TFTs), which are switching devices, are formed at intersections of the gate lines and the data lines. In addition, pixel electrodes are formed on the pixel regions.
The LCD panel is formed by attaching the array substrate and the color filter substrate with a sealant at an outer edge of an image display region. Here, the array substrate and the color filter substrate face each other. The two substrates are attached to each other with an attachment key formed on either the array substrate or the color filter substrate.
The process of fabricating the LCD panel may be divided into an array process for forming a switching device on the array substrate, a color filter process for forming a color filter on the color filter substrate and a cell process. When a LCD panel is fabricated, the LCD must be fabricated in an area which is very clean. In order to maintain cleanliness, substrates used in the fabrication of LCD panels are moved in a cassette between processes. In addition, the substrates may also be stored within a stocker for temporary storage.
FIG. 1 is a schematic sectional view that illustrates a structure of a general stocker 10.
As shown, a stocker body 15 has a box shape and a path 16 formed therein where the path 16 is in a vertical direction relative to the stocker 10. The stocker 10 includes a plurality of shelves 40 on which cassettes 30 for receiving substrates are loaded. The shelves 40 are disposed on both sides of the path 16.
A stacker 20 is installed at the path 16 which loads the cassette 30 on the shelf 40 or draws the cassette 30 from the shelf 40 for conveyance. Also, the stacker 20 includes driving units 21 and 22 which drive the stacker 20 and convey the cassette 30.
A robot arm 23 is installed at the stacker 20 for conveying the cassette 30 to each process step by loading or unloading it.
A plurality of fan filter units (FFUs) (not shown) for purifying the air and supplying the purified air into the stocker body 15 are installed on a ceiling of the stocker body 15. The FFUs are also at a ceiling of the path 16. In addition, an air introduction control shutter (not shown) for controlling the amount of air introduced into the stocker body 15 is installed at a rear side of the shelf 40.
Reference numeral 50 indicates an access floor of a clean room where the stocker 10 is installed. Reference numeral 60 indicates a loader upon which the stacker 20 loads and unloads the cassette.
A frame of the stocker body 15 is formed with a metallic material. In order to accept the cassette 30, the shelf 40 is formed with the frame. However, the stocker body 15 requires a large amount of shelves 40. Accordingly, manufacturing costs associated with the stocker 10 greatly increase.
Furthermore, if a robot of the stacker 20 collides with the frame of the stocker body 15, the frame of the stocker body may deform. Thus, the stocker 10 must be taken offline in order to complete repairs.